Wireless Notice Board: Basic Tutorial

Presently almost all electronic notice boards are designed using wired system.One of the drawbacks of the design is the system is inflexible in term of placement. The commonnotice board cannot be placed anywhere because of the messy wire. The aim of this project is to develop a wireless notice board that will be used atthe faculty in order to display latest information.

This wireless notice board project mainly focuses on transmission of textual data through air interface by the use of GSM through asynchronous serial communication. The data will be processed by the microcontroller on both ends. The data will be displayed on LCD only after entering unique pass key.

Actually what happens is, sending SMS through phone has become very popular and if we can use this SMS to control devices and in displaying data. It is possible to receive or decode the SMS globally by using GSM, by the any part of world we can control and display data on LCD board.

In this project we not only send the data but send the data with pass code also. Which enables us to prevent the unauthorized use of LCD display board and only the person who have pass code can have access to LCD board .

Basic Block Diagram:

Block Diagram of 8051 Microcontroller based Wireless Notice Board

Fig. 1: Block Diagram of 8051 Microcontroller based Wireless Notice Board

The block diagram of the project is divided into two parts

1. GSM Module

2. Controller Module

Main Module

The Main Module consists of

1. 8051 Microcontroller

2. MAX232 Circuit

3. EEPROM

4. Microsoft Hyperterminal

Reading SMS Using AT Commands

To enable a computer / PC to read SMS messages from a message storage area, the GSM/GPRS modem or mobile phone has to support either of the AT commands

+CMGR (command name in text: Read Messages),

+CMGL (command name in text: List Messages),

+CNMI (command name in text: New Message Indication).

The +CMGR AT command is used to read an SMS message at a certain location of the message storage area, while the +CMGL AT command is used to read SMS messages that have a certain status from the message storage area. The status can be “received unread”, “received read”, “stored unsent”, “stored sent”, etc.

The +CMGL AT command also allows you to retrieve all SMS messages stored in the message storage area.

Following is an example for illustrating the +CMGR, +CMGL and +CNMI.

1. Suppose you want to use your computer / PC to read a text message from the message storage area and you know the index at which the SMS text message is located. In this case, you should use the +CMGR AT command. Here is the command line to be typed (assume the SMS text message is stored at index 3)

AT+CMGR=3

The GSM/GPRS modem or mobile phone should return something like this:

+CMGR: “REC READ”,”+85291234567″,,”07/02/18,00:12:05+32″

Hello, welcome to our SMS tutorial.

Interfacing and Circuit Images

2. Suppose you are now in another situation. You want to use your computer / PC to retrieve all inbound SMS messages that have not been read before. In this case, you should use the +CMGL AT command. In SMS text mode, the command line to be used should be:

AT+CMGL=”REC UNREAD”

The GSM/GPRS modem or mobile phone should return something like this:

+CMGL: 1,”REC UNREAD”,”+85291234567″,”07/02/18, 00:05:10+32″

Reading text messages is easy.

+CMGL: 2,”REC UNREAD”,”+85291234567″,”07/02/18, 00:07:22+32″

A simple demo of SMS text messaging.

The +CMGL AT command can also be used to read all SMS messages stored in the message storage area. To do so in SMS text mode, the command line should be:

AT+CMGL=”ALL”. This time the response of the GSM/GPRS modem or mobile phone should be something like this:

+CMGL: 1,”REC READ”,”+85291234567″,,”07/02/18,00:05:10+32″

Reading text messages is easy.

+CMGL: 2,”REC READ”,”+85291234567″,,”07/02/18,00:07:22+32″

A simple demo of SMS text messaging.

+CMGL: 3,”REC READ”,”+85291234567″,,”07/02/18,00:12:05+32″

Hello, welcome to our SMS tutorial.

3. Suppose you are now in another situation. You want to use your computer / PC to get automatically notified with new inbound SMS messages that have been received. In this case, you should use the +CNMI AT command. In SMS text mode, the command line to be used should be:

AT+CNMI=2,2,2,0,0

When a new message is received then

+CMT: “+919998112112”,,”12/03/12,11:17:50:13+22”

Welcome to BVM College

Table : AT-Command Set Overview

Command	Description
AT	Check if serial interface and GSM modem is working.
ATE0	Turn echo off, less traffic on serial line.
AT+CNMI	Display of new incoming SMS.
AT+CPMS	Selection of SMS memory.
AT+CMGF	SMS string format, how they are compressed.
AT+CMGR	Read new message from a given memory location.
AT+CMGS	Send message to a given recipient.
AT+CMGD	Delete message.